1. Field of the Invention
The present invention relates to halogenation of aromatic amine compounds.
2. Description of the Background Art
Halogenated aromatic amine compounds are useful as chemical intermediates. For example, 2,4-dihaloanilines, such as 4-bromo-2-fluoroaniline, are useful, inter alia, in the preparation of pharmaceutical and agricultural chemicals. The preparation of certain of these useful chemical intermediates has previously often been cumbersome and expensive. Prior art processes for the production of 4-bromo-2-fluoroaniline, for example, may require the use of expensive and/or difficult to obtain brominating agents.
One process for the preparation of 4-bromo-2-fluoroaniline (and its use in the preparation of arylpropionic acids) is taught in U.S. Pat. No. 4,443,631 to Padilla, issued April 17, 1984. 1,3-dibromo-5,5-dimethylhydantoin in dimethylformamide (DMF) is prepared under nitrogen and is added to a solution of 2-fluoroaniline in DMF maintained at -34.degree. to -23.degree. C. with a dry ice-acetone bath. Other brominating agents reportedly useful are N-bromamides or -imides such as N-bromoacetamide or N-bromosuccinimide.
U.S. Pat. No. 3,987,057 (Goddard, Oct. 19, 1976) references the production of 4-bromo-2-fluoroaniline from 2-fluoroaniline and N-bromo-succinimide.
U.S. Pat. No. 4,138,242 (Goddard, Feb. 6, 1979) relates to herbicidal compounds and their preparation from 4-chloro-2-fluoroaniline. The 4-chloro-2-fluoroaniline is prepared through the chlorination of 2-fluoroacetanilide to yield 4-chloro2-fluoroacetanilide and the subsequent formation of the desired aniline.
There remains a need in the art for a new, simple, safe and relatively inexpensive process for the halogenation of aromatic amine compounds.